Add support for cold plugging devices, auto-loading of modules

This patch adds a new plugin to Finit called modprobe.  It probes in
/sys/devices after modalias files and then calls 'modprobe -ab' for
each alias listed.

For hot-plugging we recommend adding the following to /etc/mdev.conf

  $MODALIAS=.*	root:root	0660	@modprobe -b "$MODALIAS"

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

plugins/Makefile.am

@@ -7,7 +7,7 @@ AM_CPPFLAGS        += $(lite_CFLAGS)
 
 if STATIC
 noinst_LTLIBRARIES  = libplug.la
-libplug_la_SOURCES  = bootmisc.c rtc.c initctl.c pidfile.c procps.c tty.c urandom.c
+libplug_la_SOURCES  = bootmisc.c modprobe.c rtc.c initctl.c pidfile.c procps.c tty.c urandom.c
 
 if BUILD_ALSA_UTILS_PLUGIN
 libplug_la_SOURCES += alsa-utils.c
@@ -52,7 +52,7 @@ libplug_la_SOURCES += resolvconf.c
 endif
 
 else
-pkglib_LTLIBRARIES  = bootmisc.la rtc.la initctl.la pidfile.la procps.la tty.la urandom.la
+pkglib_LTLIBRARIES  = bootmisc.la modprobe.la rtc.la initctl.la pidfile.la procps.la tty.la urandom.la
 
 if BUILD_ALSA_UTILS_PLUGIN
 pkglib_LTLIBRARIES += alsa-utils.la

plugins/modprobe.c

@@ -0,0 +1,176 @@
+/* Coldplug modules using modalias magic
+ *
+ * Copyright (c) 2020  Joachim Nilsson <troglobit@gmail.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/*
+ * Cold plug magic taken from Buildroot
+ * https://github.com/buildroot/buildroot/commit/b4fc5a180c81689a982d5c595844331684c14f51
+ *
+ * The plugin basically does this, only in C:
+ *
+ * 	system("find /sys/devices -name modalias -print0"
+ *             "     | xargs -0 sort -u -z"
+ *             "     | xargs -0 modprobe -abq");
+ *
+ * Note: BusyBox must *not* be built with CONFIG_MODPROBE_SMALL
+ */
+
+#include <fnmatch.h>
+#include <ftw.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/time.h>		/* gettimeofday() */
+#include <sys/types.h>
+#include <lite/lite.h>
+
+#include "config.h"
+#include "finit.h"
+#include "helpers.h"
+#include "plugin.h"
+
+struct module {
+	TAILQ_ENTRY(module) link;
+	char *alias;
+};
+
+static TAILQ_HEAD(, module) modules  = TAILQ_HEAD_INITIALIZER(modules);
+
+static int modprobe(char *alias)
+{
+	char *args[] = {
+		"modprobe",
+		"-abq",
+		alias,
+		NULL,
+	};
+	pid_t pid;
+
+	pid = fork();
+	switch (pid) {
+	case -1:
+		_pe("Failed forking modprobe child");
+		return 1;
+	case 0:
+		execvp(args[0], args);
+		break;
+	default:
+		if (!complete(args[0], pid))
+			_d("Successful modprobe of %s", alias);
+		break;
+	}
+
+	return 0;
+}
+
+static void alias_add(char *alias)
+{
+	struct module *m;
+
+	m = malloc(sizeof(*m));
+	if (!m)
+		return;
+	m->alias = strdup(alias);
+	if (!m->alias) {
+		free(m);
+		return;
+	}
+
+	TAILQ_INSERT_TAIL(&modules, m, link);
+}
+
+static void alias_remove(struct module *m)
+{
+	TAILQ_REMOVE(&modules, m, link);
+	free(m->alias);
+	free(m);
+}	
+
+static int alias_exist(char *alias)
+{
+	struct module *m;
+
+	TAILQ_FOREACH(m, &modules, link) {
+		if (!strcmp(m->alias, alias))
+			return 1;
+	}
+
+	return 0;
+}
+
+static int scan_alias(const char *path, const struct stat *st, int flag, struct FTW *unused)
+{
+	FILE *fp;
+	char buf[256];
+
+	if (fnmatch("*/modalias", path, 0))
+		return 0;
+
+	fp = fopen(path, "r");
+	if (!fp)
+		return 0;
+	if (fgets(buf, sizeof(buf), fp)) {
+		chomp(buf);
+		if (!alias_exist(buf))
+			alias_add(buf);
+	}
+	fclose(fp);
+
+	return 0;
+}
+
+static void coldplug(void *arg)
+{
+	struct module *m, *tmp;
+	int rc = 0;
+
+	print_desc("Cold plugging system", NULL);
+	nftw("/sys/devices", scan_alias, 200, FTW_DEPTH);
+	TAILQ_FOREACH_SAFE(m, &modules, link, tmp) {
+		rc += modprobe(m->alias);
+		alias_remove(m);
+	}
+
+	print_result(rc);
+}
+
+static plugin_t plugin = {
+	.name = __FILE__,
+	.hook[HOOK_BASEFS_UP] = { .cb  = coldplug },
+	.depends = { "bootmisc", }
+};
+
+PLUGIN_INIT(plugin_init)
+{
+	plugin_register(&plugin);
+}
+
+PLUGIN_EXIT(plugin_exit)
+{
+	plugin_unregister(&plugin);
+}
+
+/**
+ * Local Variables:
+ *  indent-tabs-mode: t
+ *  c-file-style: "linux"
+ * End:
+ */